The present invention relates an optical beam drift compensation apparatus and method for monitoring a beam position and optically compensating for changes in position of the beam so as to direct the laser beam along a desired optical path. The invention finds particular utility in connection with all manner of laser beam applications wherein a laser beam is delivered to a workpiece or other target to be processed, including industrial and other laser applications. Exemplary applications include laser machining, drilling, ablation, and so forth, illumination, photobonding or photocuring applications, and other laser processing applications. It will be recognized that the present invention may be employed with all manner of optical systems wherein it is necessary or desired to deliver a laser or other collimated ray path to a precise target location or otherwise maintain a precise propagation path.
The direction or position of a laser beam tends to drift over time for a number of reasons, including thermal effects within the laser source, fluctuations in air density, vibration or movement of the surface or platform carrying the laser source, movement, vibration, or thermal effects on the optical components in the optical train. Laser beam drift compensation systems are known which employ a beam splitter to direct a portion of the beam to a photosensitive position sensor, such as quadrant detector. Any difference between the detected position and the anticipated or desired position are corrected using complex and expensive electro-optic devices. See, for example, U.S. Pat. No. 5,315,111. Passive techniques for stabilizing the beam position and direction typically rely on vibration isolation and the use of components which minimize thermal effects. Such techniques, however, are very expensive and are of limited effectiveness. See, for example, U.S. Pat. Nos. 5,315,111 and 5,923,418. Accordingly, the present invention contemplates a new and improved apparatus and method for compensating for beam drift compensation employing inexpensive, passive optical devices.